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Getting Started

Why do we have Node?

The web is very stringy, Swift is very type-safe, this is a major problem when doing web development in Swift. Node is our attempt at providing a solution to this problem.

What is Node?

Node is a data abstraction with an emphasis on being an intermediary between distinct types. For example, json from a client might use node to convert between the JSON and itself.

How do I use it?

Node can be a little different to work with at first if you're familiar with less type-safe languages, let's look at a couple of examples and how we might start using Node in our projects. Most often, we'll be working with Node conversions.

NodeInitializable

NodeInitializable can be read and understood as An object that can be initialized with a Node. Let's look at a simple implementation.

struct Person: NodeInitializable {
    let name: String
    let age: Int

    init(node: Node) throws {
        name = try node.get("name")
        age = try node.get("age")
    }
}

Now that we have this, we can easily convert abstract data to a Person. Here's how that might look:

let person = try Person(node: json)

Note: There are some more advanced functionality options for JSON and database Row types in particular, we'll cover that later.

By conforming our Person object to NodeInitializable, we can also use more advanced cases such as arrays:

let people = try [Person](node: jsonArray)

NodeRepresentable

NodeRepresentable can be read and understood as An object that can be represented as a Node. Let's take a look at a simple implementation. We'll stick with the Person example above

extension Person: NodeRepresentable {
    func makeNode(in context: Context) throws -> Node {
        var node = Node(context)
        try node.set("name", name)
        try node.set("age", age)
        return node
    }
}

Now that we've done this, we can easily convert our person or a collection of Person objects into a Node.

let node = try person.makeNode(in: nil)

And also for collections, like arrays

let node = try [kim, joe, jan].makeNode(in: nil)

Context

Up to this point, we've seen Context a lot, but what's it for. When we're serializing or mapping an object, we might have a lot of different situations we're mapping differently for. Maybe one is for the database, one is for the view, one is for JSON, etc.

If you're using Vapor, we provide a lot of contexts and more native integration options, but here's how one might define their own.

import Node

final class MyContext: Context {
}

let myContext = MyContext()

extension Context {
    var isMyContext: Bool {
        return self is MyContext
    }
}

Now inside our object, we could add special behavior.

extension Person: NodeRepresentable {
    func makeNode(in context: Context) throws -> Node {
        var node = Node(context)
        try node.set("name", name)
        try node.set("age", age)
        if context.isMyContext {
            try node.set("special-attribute", special)
        }
        return node
    }
}

We might call it like this:

let specialNode = person.makeNode(in: myContext)

This is a common usage, but can be adapted for any scenario where we require special metadata to help us properly serialize or map our object.

NodeConvertible

NodeConvertible is simply the combination of Representable and Initializable. These objects can be converted easily to and from node. Taking our Person object from earlier, we should be able to do this:

// ..
let node = person.makeNode(in: myContext)
let back = try Person(node: node)
print("\(person) went to node and back to \(back)")